This invention relates to a composite material having metal nanoparticles dispersed in a polysilylenemethylene (this polymer may also be called polysilmethylene), of which use is expected as an optical functional material, and to a process for the production thereof.
As metal nanoparticles or semiconductor nanoparticles having size of nanometer order shows non-linear optical effects, a composite material having the nanoparticles dispersed in polymer or glass matrix is drawing attention as an optical functional material. One known method of preparing such a composite material is a vapor phase method in which nanoparticles of a metal or a semiconductor, which have been produced by vacuum deposition, sputtering or CVD, are covered with an inert substance by sputtering. Another known method includes dispersing nanoparticles of a metal or a semiconductor in a porous glass formed by a sol-gel method. In a further known method, such nanoparticles of semiconductor are prepared simultaneously with a sol-gel glass and are dispersed therein. In addition to the above three ordinary methods, there are known methods in which into a metallic semiconductor component previously dispersed in a polymer another component element is introduced, and it is subject to irradiation with a laser beam to selectively form nanoparticles, and a method in which a polymer film, which is thermodynamically in stable condition, is heated in contact with a metal film to stabilize the polymer and to disperse the metal in form of nanoparticles into the polymer film.
The conventional dispersion matrix system of nanoparticles has such a problem that as the nanoparticle has high surface energy, it is not necessarily inert to a matrix, and it is apt to form a chemical bond between the surface thereof and the matrix to cause to change state of the nanoparticle from the original state. Another problem of the conventional methods is that the nanoparticles are apt to form aggregates in the matrix, so that the composite material fails to show satisfactory non-linear characteristics and causes light scattering.
It is, therefore, an object of the present invention to provide a composite material in which nanoparticles of a metal are dispersed in a chemically inert polymer.
Another object of the present invention is to provide a composite material having the nanoparticles dispersed therein, in which aggregation among the metal nanoparticles is inhibited with the chemically inert material.
It is a further object of the present invention to provide a composite material having the nanoparticles dispersed therein, in which the optical effects by the nanoparticles are enhanced by forming multi-layers of the nanoparticle dispersing layer, so that a higher content of the nanoparticle may be present.
It is yet a further object of the present invention to provide a composite material having the nanoparticles dispersed therein, in which a region having a higher content of the nanoparticles and a region having no or much less content of the nanoparticle are alternately arranged so that the composite material can function as a diffraction grating.
It is yet a further object of the present invention to provide a process which can easily produce the above composite material.
In accomplishing the foregoing object, there is provided in accordance with the present invention a composite material comprising a laminate formed by laminating a plurality of polysilylenemethylene layers in which nanoparticles of a metal are dispersed in an inside region adjacent to a top surface thereof, the metal being selected from the group consisting of gold, platinum, palladium, copper and silver.
In another aspect, the present invention provides a process for producing a composite material having nanoparticles of a metal dispersed, comprising the steps of:
(a) forming, on a substrate, a layer of disilacyclobutane capable of providing polysilylenemethylene via ring open polymerization:
(b) forming a layer of nanoparticles of a metal selected from the group consisting of gold, platinum, palladium, copper and silver on a surface of said disilacyclobutane layer obtained in step (a);
(c) heating said disilacyclobutane layer, on which said nanoparticle layer has been formed in step (b), at the temperature capable of polymerizing said disilacyclobutane but not higher than the melting point of the polysilylenemethylene derived from said disilacyclobutane, thereby forming a first polysilylenemethylene layer in which said nanoparticles are dispersed in an inside region adjacent to a surface thereof;
(d) forming another layer of disilacyclobutane on the first polysilylenemethylene layer obtained in step (c), said disilacyclobutane capable of providing polysilylenemethylene via ring open polymerization;
(e) forming a layer of nanoparticles of a metal selected from the group consisting of gold, platinum, palladium, copper and silver on a surface of said disilacyclobutane layer obtained in step (d); and
(f) heating said disilacyclobutane layer, on which said nanoparticle layer has been formed in step (e), at the temperature capable of polymerizing said disilacyclobutane but not higher than the melting point of the polysilylenemethylene derived from said disilacyclobutane, thereby forming a second polysilylenemethylene layer, in which said nanoparticles are dispersed in an inside region adjacent to a surface thereof.
A cycle of the above steps (d) through (f) is repeated at least two times, thereby forming a laminate of three or more polysilylenemethylene layers each, in which said nanoparticles are dispersed in an inside region adjacent to a surface thereof.